I'm a huge fan and avid user of PortableApps.com and their offerings of apps. It would be very helpful to allow installation to portable storage, like USB drives. You can obviously still keep your existing security via registration code, but it would be so helpful to be able to backup my entire copy of BTP and if need be bring to a new computer of mine without hassle.

I personally keep regular backups of my portable app installs and backup to 2 separate thumb drives. All in case my HDD crashes or whatever. I can just plug-in and go without disruption.